Carbon black is useful in many applications. For various applications, it is desirable to use carbon black with modified properties. In particular, for use in aqueous compositions, e.g., it is desirable to use modified carbon black with ionic groups provided on the surface thereof to facilitate dispersion of the carbon black in the aqueous composition. Some processes for chemically changing the surface of carbon black are known and used commercially. For example, it is well known that a carbon black surface can be oxidized with a variety of treating agents. Surface oxidation is used to make some commercial products. Sulfonation using sulfuric acid or chlorosulfuric acid and halogenation of a carbon black surface are also known.
U.S. Pat. No. 3,043,708 describes modified carbon blacks having hydrocarbon groups chemically attached to the surface of the carbon black. The modified carbon blacks are prepared by reacting carbon black with an alkylating agent in the presence of a Friedel-Crafts type reaction catalyst. The hydrocarbon groups which reportedly can attach to the surface of the carbon black include aliphatic and aromatic groups. U.S. Pat. No. 3,025,259 describes rubber compositions containing the modified carbon blacks of U.S. Pat. No. 3,043,708.
U.S. Pat. No. 3,335,020 describes modified carbon blacks where the carbon black is treated with benzene which is then polymerized on the carbon black.
U.S. Pat. Nos. 2,502,254 and 2,514,236 describe the manufacture of pigments containing carbon black. U.S. Pat. No. 2,502,254 reports that highly dispersed pigments suitable for mass pigmentation of viscose can be obtained by generating an azo pigment in the presence of carbon black. The pigment is produced by coupling a diazotized amine and another usual intermediate for a yellow, orange, or red pigment in the presence of carbon black in one or the other of the aqueous solutions of which the mixing brings about the coupling. U.S. Pat. No. 2,514,236 reports that this process can also prepare a chocolate brown pigment by coupling one molecular proportion of a tetrazotized benzidine with two molecular proportions of an arylmethyl pyrazolone in the presence of carbon black.
PCT Patent Application No. WO 92/13983 describes a process for modifying the surfaces of carbon-containing materials by electrochemical reduction of diazonium salts. The process is reportedly applicable, in particular, to carbon plates and carbon fibers for composite materials. Carbon-containing materials modified by the process are also described.
U.S. Pat. No. 5,851,280 describes processes for preparing carbon black product having an organic group attached to the carbon black wherein a diazonium salt reacts with the carbon black in the absence of an externally applied electric current sufficient to reduce the diazonium salt, or wherein a diazonium salt reacts with the carbon black in a protic reaction medium.
U.S. Pat. App. Pub. No. 2008/0115695 describes a method of producing modified pigment by sulfonating a pigment and subsequently oxidizing the pigment, whereby the modified pigment may have sulfonic acid and carboxylic surface modifying groups attached to the surface of the pigment.
U.S. Pat. App. Pub. No. 2010/0061951 describes a method of making surface modified or self-dispersing pigment by reacting a substituted triazine compound (e.g., a tris-arylamino-1,3,5-triazine compound) with an aqueous pigment dispersion.
Inkjet printing is a non-impact method for producing printed images by the deposition of ink droplets in a pixel-by-pixel manner to an image-recording element in response to digital data signals. There are various methods that may be utilized to control the deposition of ink droplets on the image-recording element to yield the desired printed image. In one process, known as drop-on-demand inkjet, individual ink droplets are projected as needed onto the image-recording element to form the desired printed image. Common methods of controlling the projection of ink droplets in drop-on-demand printing include piezoelectric transducers and thermal bubble formation. In another process, known as continuous inkjet, a continuous stream of droplets is charged and deflected in an image-wise manner onto the surface of the image-recording element, while un-imaged droplets are caught and returned to an ink sump. Inkjet printers have found broad applications across markets ranging from desktop document and photographic-quality imaging, to short run printing and industrial labeling.
Pigment-based inkjet inks are often preferred over dye-based inkjet inks because of the superior image stability typically observed with the pigment-based inks. Self-dispersed pigments in turn are often preferred over surfactant-dispersed, oligomer-dispersed or polymer-dispersed pigments because of their greater stability to a variety of ink formulations and environmental keeping conditions. Self-dispersed pigments are typically used when high density and sharp images are required such as for the printing of text and graphics, and are especially useful when printing on plain papers (i.e., papers not specifically designed to render photographic quality images).
Despite the technologies discussed above, there remains a desire for additional methods for modifying the surface chemistry of carbon black to impart desired properties to the carbon black. In particular, there remains a desire for additional methods for modifying the surface chemistry of carbon black to impart increased hydrophilicity and self-water dispersibility to carbon black pigments for use in aqueous inks.